Vehicle Positioning in High-Reflection Environments

Abstract

A positioning system obtains an estimate of the heading of a body whose position or velocity is to be estimated, for example from a heading sensor such as a gyroscope or accelerometer. Respective signals are tracked from a plurality of transmitters, and a respective Doppler measurement is obtained from each of said tracked signals. For each of the tracked signals, a speed of the body is estimated using the estimate of the heading of the body and the respective Doppler measurement. It is then determined whether the estimated speed of the body is consistent with the signal having been received along a direct path from the transmitter. Signals that provide information about the speed of the body that is inconsistent with the signal having been received along a direct path from the transmitter are then disregarded when estimating the position or velocity of the body.

1 . A method of operation of a positioning system, the method comprising:
 obtaining an estimate of the heading of a body whose position or velocity is to be estimated;   tracking respective signals from a plurality of transmitters;   obtaining a respective Doppler measurement from each of said tracked signals;   for each of said tracked signals, estimating a speed of said body using the estimate of the heading of the body and the respective Doppler measurement, determining whether the estimated speed of the body is consistent with the signal having been received along a direct path from the transmitter; and   disregarding signals that provide information about the speed of the body that is inconsistent with the signal having been received along a direct path from the transmitter, when estimating the position or velocity of the body.   
     
     
         2 . The method of  claim 1 , further comprising:
 determining whether the estimated speed of the body is consistent with the signal having been received along a direct path from the transmitter by determining whether the estimated speed of the body suggests that the respective signal was obtained from the transmitter via a reflection.   
     
     
         3 . The method of  claim 1 , further comprising:
 determining whether the estimated speed of the body is consistent with the signal having been received along a direct path from the transmitter by comparing the estimated speed of the body in the direction of said estimated heading with a threshold speed.   
     
     
         4 . The method of  claim 3 , wherein the threshold speed is zero, such that it is determined that the estimated speed of the body is not consistent with the signal having been received along a direct path from the transmitter if the estimated speed of the body in the direction of said estimated heading is negative. 
     
     
         5 . The method of  claim 3 , wherein the threshold speed is adaptable, based on an angle between the estimated heading of the body whose position or velocity is to be estimated and the direct path from the transmitter. 
     
     
         6 . The method of  claim 1 , wherein the estimate of the heading of the body is based on a signal received from a heading sensor provided on the body. 
     
     
         7 . The method of  claim 6 , wherein the signal from the heading sensor further comprises information about the speed of the body, the method further comprising determining whether the estimated speed of the body obtained using the estimate of the heading of the body and the respective Doppler measurement is consistent with the signal having been received along a direct path from the transmitter by comparing said estimated speed of said body obtained using the estimate of the heading of the body and the respective Doppler measurement with the information about the speed of the body obtained from the heading sensor. 
     
     
         8 . The method of  claim 1 , further comprising obtaining the estimate of the heading of the body immediately after determining that the body has started moving after being determined to be stationary. 
     
     
         9 . The method of  claim 1 , further comprising:
 preventing future tracking of disregarded signals.   
     
     
         10 . The method of  claim 1 , further comprising:
 using measurements from the signals that are not disregarded to update a position/velocity/time solution for the body.   
     
     
         11 . The method of  claim 1 , wherein the heading sensor comprises a gyroscope, having a known positional relationship to the body for indicating an orientation of the body. 
     
     
         12 . The method of  claim 11 , wherein the heading sensor further comprises a temperature sensor for calibrating an output of the gyroscope. 
     
     
         13 . The method of  claim 10 , further comprising an accelerometer, for indicating a direction of motion of the body. 
     
     
         14 . The method of  claim 1 , wherein the heading sensor comprises a magnetometer, for indicating a direction of motion of the body. 
     
     
         15 . A positioning system, comprising:
 a heading sensor, for generating an estimate of the heading of a body whose position or velocity is to be estimated;   a receiver, for tracking respective signals from a plurality of transmitters; and   a processor, for deriving a respective Doppler measurement from each of said tracked signals;   wherein a respective speed derived from said Doppler measurement of each of said tracked signals is tested for consistency with said heading.   
     
     
         16 . The positioning system of  claim 15 , wherein signals having a Doppler-measurement-derived speed consistent with the signal having been received along a direct path from a respective transmitter of said plurality of transmitters are consistent with said heading. 
     
     
         17 . The positioning system of  claim 16  wherein signals having a Doppler-measurement-derived speed inconsistent with the signal having been received along a direct path from a respective transmitter of said plurality of transmitters are disregarded. 
     
     
         18 . The positioning system of  claim 15  wherein the heading sensor comprises a gyroscope, having a known positional relationship to the body, for indicating an orientation of the body. 
     
     
         19 . The positioning system of  claim 18 , wherein the heading sensor further comprises a temperature sensor, for calibrating an output of the gyroscope. 
     
     
         20 . The positioning system of  claim 19 , wherein the heading sensor comprises a magnetometer, for indicating a direction of motion of the body.